Fuse plug



May 25, 1937. B. F. MULDOON 2,081,675

' FUSE PLUG Filed A ril 10, 1934 ATTORNEYS Patented May 25, 1937 UNITED STATES *PATENT OFFICE FUSE PLUG Application April 10, 1934, Serial No. 719,834

9 Claims.

This invention relates to a fuse plug that is so constructed that a user can easily recognize when the fuse has blown.

In carrying out the invention a member of resilient material is installed in the plug under tension and is maintained under tension by means of fusible metal, that is preferably weak ened at one point. Signal means has a portion visible indicating that the fuse plug is all right when this is true. When the fuse blows the member of resilient material moves to the position toward which it is biased, thereby moving the signal means to another position or bringing into view of the observer 2. signal or indication showing that the fuse has blown. The fusible material and the resilient member are so connected that they are in series in the electric circuit when the fuse plug is in place.

The invention will be described in connection with a fuse plug of the screw type, but it is understood that it is not restricted to this particular type of screw plug.

The invention will be understood from the description in connection with the accompanying drawing in which Fig. 1 is an end view of an illustrative embodiment of the invention; Fig. 2 is a longitudinal section through Fig. 1; Fig. 3 is a section along the line 3-4 of Fig. 2; Fig. 4; is a section along the line 4-4 of Fig. 2; Fig. 5 is a section along the line 55 of Fig. 2; Fig. 6 is a plan view of one of the details and Fig. '7 is a sectional view of one of the details partly broken away.

In the drawing reference character I indicates a body of rigid insulating material, such as por celain, for example, that is provided with threads 2 upon which a metallic screw shell 3 may be screwed. The body I is provided with a shoulder and the shell 3 is provided with a flange 3' which bears against this shoulder when the shell is in place. The body I may also be provided with another shoulder against which the other end of the shell 3 may press when it is in place. The body I is provided with diametrically spaced lugs 4 that are preferably, though not necessarily, integral with the body l. The end 5 of the body I that carries the lugs 4 is enlarged and a metal cap 6 is installed on this enlarged end and is kept in place by having its rim 1 pressed inwardly to contact with a shoulder on the enlarged portion 5. The lugs 4 of insulating material extend through holes or openings in the cap 6 and are available for the user to install and remove the plug without touching the metal cap 6, or without grasping the rim of the plug, thus reducing the hazard of injury from escaping flame. A wrench may be applied to the lugs 4 for inserting or removing the plug, if desired.

A central opening or recess 8 is provided in the body I. This opening 8 may be enlarged on one side, as shown at 9 in Fig. 2, or the recess 8 may be conically shaped. An opening [ii is provided along the other side of the recess 8 from the portion 9 to accommodate a fuse strip II. The fuse strip H is provided with a reduced or weakened portion [2 so that it will melt at this point when an overload occurs.

A member I3 of resilient metal, such as a strip of brass, for example, extends into the opening 3 and is connected to the end of the fuse strip ii. The strip 13 may be connected to the strip l l, for example, by having lugs l4 along its sides which may be bent around a down-turned end of the strip II to clamp it in position.

An opening 15, which is reduced in size compared to the opening 8, is provided at the end of the body l opposite the cap 6 and is countersunk at its outer end, as indicated at 46.

The strip i3 is bent before it is installed so as to cause it to spring into the enlargement 9 when the fuse blows. One end of the strip I3 is enlarged in the form of a square and a central square opening H is cut out of this square portion to leave narrow marginal portions, as indicated at I8 in Figs. 2 and 5. The strip l3 has a double bend near the portion It, as shown at 19 in Fig. 2. The opening iii in the body I is widened along one side, as shown at 20, so that the portion i8 can be passed through it from the opening 8 and then bent into the position shown in Fig. 2.

The center contact for the plug may be made in the form of a rivet from a sheet of metal 2| cut out as indicated in Fig. 6. It is cut out to leave a central circular portion 22 and a plurality of radially extending arms or prongs 23. These prongs are bent, as shown at 24, to extend perpendicular to the circular portion 22, the circular portion 22 being of greater diameter than the distance across the opening i5.

The fuse strip H and the resilient strip l3 are installed with the outer end of the fuse strip ll secured between the shell 3 and the threads 2, and with the outer portion of the strip [3 in place between a prong 23 and a side of the opening l5 and the ends of the other prongs 23 are bent over, as shown at 25, against the bottom of the recess 8.

A strip or sheet 25 of paper or similar material is installed between the cap 6 and the end 5 of the body I. A strip 26 of mica or other transparent material is placed along the underside of the paper 25. This strip of paper 25 is provided with an opening 21 near its middle and an opening 28 is provided in the cap 6 larger than the opening 21 so that portions of the paper 25 are visible through the opening 28 and may bear insignia, legends or advertisements as shown by 15 and Amp. in Fig. 1.

A folded strip 29 of resilient material (Figs. 2 and 7), such as paper, for example, is provided with overlapping edges 30 and 3I and is connected to the end of the strip I3 so as to be moved when the end of this strip moves. The strip 29 may be connected to the strip I3 by the end of this strip I3 passing through holes 32 in the overlapping edges and then being bent as shown at 33 in Fig. 2, or the end of the strip I3 may be reduced and passed through these holes with the shoulders 34 at the end of the reduced portion in contact with the outer surface of the outer overlapping edge of the strip 29, as shown in Fig. 7. The springiness of the strip 29 will keep the main body portion thereof pressed against the inner side of the mica strip 26 in all positions of the strip I3. The surface of the strip 29 that is exposed to view through the opening 28, mica strip 26 and opening 2'! is provided with the letters 0. K. and N. G. at such places on the strip that the letters 0. K. are exposed to view through the opening 28, opening 21 and mica strip 26 when the strip I3 is in the position shown in Fig. 2, and the letters N. G. are exposed to view when the strip I3 is in the position shown in dotted lines in Fig. 2.

In view of the fact that so long as the fuse strip H is intact the strip I3 will be held under tension in the position shown in Fig. 2, the O. K. sign will be visible until the fuse blows and as soon as it blows the strip I 3 will spring into the position shown in the dotted line position in Fig. 2, thus exposing to view the letters N. G..

I claim:

1. In a fuse plug, a member of resilient metal installed under tension and serving as a portion of the electric circuit, fusible metal connected to said resilient member and maintaining it under tension, and signal means connected to said resilient member, said signal means comprising a folded strip of resilient material carried by said resilient member.

2. In a fuse plug having a cap with an opening therethrough, a sheet of non-transparent material in said cap larger than said opening having an opening therethrough smaller than the opening through the cap, and a sheet of transparent material in said cap extending across said lastnamed opening.

3. In a fuse plug having a cap with an opening therethrough, a resilient signal carrying means in said plug having a surface for receiving insignia and being visible through said opening, and a current carrying element in said plug to which said signal carrying means is pivotally connected and by which it is moved in proximity to the bottom of said cap.

4. In a fuse plug having a cap with an opening therethrough, a sheet of non-transparent material in said cap larger than said opening having an opening therethrough smaller than the opening through the cap having insignia on its exposed side visible through the opening in said cap.

5. In a fuse plug, a member of resilient material installed under tension as a part of the electric circuit and a center contact for said plug extending through an enlarged end of said member, said plug having a widened slot near one end to permit passage of said enlarged end.

6. In a fuse plug, a member of resilient conductive material installed as a part of the electric circuit, and folded strip of resilient non-conductive material with overlapping edges having signal indicia thereon, said strip being carried by a portion of said member extending through overlapping edges thereof.

'7. In a fuse plug having an opening therein, a mica strip across one end of the opening in said plug, a member of resilient conductive material installed as a part of the electric circuit, and resilient non-conductive material with signal indicia thereon carried by said member and kept by its springiness in contact with said mica strip.

8. In a fuse plug, a strip of resilient metal forming a part of the electric circuit, a fuse strip having a bent end, and lugs on said first named strip bent around the bent end of said fuse strip to connect them together, said strip of resilient metal having a reduced free end, and a folded sheet of paper that carries signalling insignia through the folded edges of which said reduced end projects.

9. In a. fuse plug, a strip of resilient metal forming a part of the electric circuit, a fuse strip having a bent end, and lugs on said first named strip bent around the bent end of said fuse strip to connect them together.

BERNARD F. MULDOON. 

